Thread grinding machine



Sept. 24, 1963 J. L. SCHOHL THREAD GRINDING MACHINE 6 Sheets-Sheet 1 Filed Oct. 12, 1961 FIG.

INVENTOR.

JOHN L. SCHOHL BY FIG. 2

ATTORN E YS Sept. 24, 1963 J. L. SCHOHL THREAD GRINDING MACHINE 6 Sheets-Sheet 2 Filed Oct. 12, 1961 FIG. 3

FIG. 7

INVENTOR.

JOHN L. SCHOHL BY AT TORNEYS Sept. 24, 1963 J. L. SCHOHL' THREAD GRINDING MACHINE 6 Sheets-Sheet 3 Filed Oct. 12, 1961 FIG. 4

INVENTOR.

JOHN L. SCHOHL By 3 fig My,

FIG.8

ATTORNEYS Sept. 24, 1963 J. 1.. SCHOHL THREAD GRINDING MACHINE 6 Sheets-Sheet 4 Filed Oct. 12, 1961 FIG.

INVENTOR.

JOHN L. SCHOHL ATTORNEYS Sept. 24, 1963 J. SCHOHL 3,104,505

THREAD GRINDING MACHINE Filed Oct. 12, 1961 e Sheets-Sheet 5 INVENTOR. JOH N L. SCHOHL ATTORNEYS Sept. 24, 1963 J. 1.. SCHOHL THREAD GRINDING MACHINE 6 Sheets-Sheet 6 Filed Oct. 12, 1961 INVENTOR.

JOHN L. SCHOHL ATTORNEYS United States Patent The present invention relates to a thread grinding machine and more particularly to a mechanism for converting a conventional lathe to a thread grinding machine.

Most small and moderate size machine tool shops and firms have one or more conventional metal cutting lathes which can be used satisfactorily for thread cut-ting; however, this operation on the conventional lathe is slow, tedious, unduly time consuming, and limited in its application by the hardness of the metal, such that it renders small and moderately sized firms noncompetitive or capable of performing only a portion of the normally required work in the field. Thread grinding machines are available as separate units for firms of this size, but these machines are relatively expensive and the firms can not justify the expense in view of the rather limited use for them in their normal operation. It is therefore one of the principal objects of the present invention to provide a relatively simple mechanism for converting the conventional metal cutting lathe to a thread grinding machine, which can be readily mounted on and removed from the lathe without making any substantial or permanent alterations in the construction of the lathe.

Another object of the present invention is to provide a thread grinding conversion unit for conventional lathes which consists of one or two pieces, easily assembled and mounted mechanisms, which will perform thread grinding operations as effectively and with the use of substantially the same procedure as the conventional thread grinding machine.

Still another object of the invention is to provide a mechanism for converting conventional metal cutting lathes to thread grinding machines, which can use either a single or multiple rib grinding wheel and which includes a mechanism for effectively dressing the wheel without disassembling the grinding mechanism and without any substantial downtime being required.

Still another object is to provide a thread grinding attachment for a lathe which requires little skill or practice in order to make satisfactory threaded products and which can be mounted on and connected to any standard or conventional lathe without the use of any special tools or equipment other than those used in conjunction with the thread grinding mechanism.

Additional objects and advantages of the invention will become apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a perspective view of a conventional metal cutting lathe showing my thread grinding mechanism mounted thereon in operating position;

FIGURE 2 is an enlarged perspective view of the present thread grinding mechanism show-ingit removed from the lathe;

FIGURE 3 is a front elevational view of the present thread grinding mechanism showing it removed from the lathe;

FIGURE 4 is a side elevational view of the thread grinding mechanism removed from the lathe;

1 IGURE 5 is a rear elevational view of the thread grinding mechanism showing it removed from the lathe;

FIGURE 6 is a top plan view of the present thread grinding mechanism;

FIGURE 7 is an enlarged fragmentary cross sectional view of the present thread grinding mechanism, the section being taken on line 7-7 of FIGURE 3;

3,104,505 Patented Sept. 24, 1963 FIGURE 8 is a cross sectional view of the thread grinding mechanism, taken on line 88 of FIGURE 4;

FIGURE 9 is a fragmentary top plan view of the thread grinding mechanism shown in the preceding figures showing the manner in which the dressing device mounted on the mechanism performs the dressing operation;

FIGURE 10 is a perspective view of a portion of the dressing device shown in FIGURE 9;

FIGURE 11 is a front elevational view of a speed reducer adapted to be attached to the head of the lathe, the reducing gears of the unit being shown in broken lines; and

FIGURE 12 is a vertical cross sectional view of the reducer unit shown in FIGURE 11, taken on line 12-12 of the latter figure.

Referring more specifically to the drawings and to FIGURE 1 in particular, a conventional metal cutting lathe is shown in perspective, consisting of bed 20, head stock 22, tail stock 24, carriage 26, compound rest 27, plate 28, dead center 30, \and wheel 32, lock lever 34, and cabinet leg 36' at one end and legs 38 and 40 at the other end of the lathe. The present thread grinding mechanism is shown at numeral 42, and a speed reducer mechanism used in conjunction with the present thread grinding mechanism and forming a part thereof is shown at numeral 44. The present thread grinding mechanism is shown mounted on compound rest 27 and movable therewith inwardly and outwardly to and from the work piece by the usual lathe controls, and movable along the work piece by the feed screw 46. Since the lathe shown in FIGURE 1 is considered conventional for the purpose of the present description, further details thereof will not be included herein.

The present thread grinding mechanism 42 consists of a compound base 50, an upper section 52 and a lower section 54 adapted to slide relative to one another, a body 56 mounted on and rigidly secured to upper section 52, a motor -58 mounted on body 56, and a mandrel 60 having a grinding wheel 62 mounted on shaft 64 and driven by motor '58 through pulleys 66 and 68 on the motor and mandrel, respectively, and belt 70. The tension on belt 70 may be varied by shifting the motor mount 72 up- Wardly or downwardly as required, the mount consisting of a plate 74 pivoted to the body 56 by a pivot means 76 including projections 78 and 80 and shaft 82 extending through the two projections. Plate 74 is tilted upwardly and downwardly and held in its adjusted position by bolt and nut 84 and 86, respectively, the bolt being pivotally secured to body 56 by a hinged portion 88.

The mandrel and motor are mounted on platform forming a par-t of body 56, the platform being secured to the main body portion 91 by an arcuately shaped dovetail joint 92, groove 93 of the joint being in main body portion 91 and the tongue 94 in the platform. The pivot point of the platform is the center of wheel 62 and the entire platform rotates or oscillates in adjusting the angular position "of wheel 62 with respect to the work piece in the lathe on which the thread grinding is being performed. A locking bolt or means 95 is provided for retaining the platform in fixed position after it has been adjusted to the desired position using the scale 96 on the main body portion 91 and on platform 90.

With the platform mounted on the main body portion in the manner described above, any desired thread pitch can be obtained within a relatively broad range by setting the platform 90 and wheel 62 with the desired angularity relative to the work piece, and by varying the speed of the feed screw 46. The wheel 62 is supported by the platform and is mounted on shaft 64 and secured thereto by an abutment 98 and nut 100 threaded onto the shaft on the end opposite pulley 68.

The base sections 52 and 54 are adjusted relative to one another for positioning the wheel vertically with respect to the work piece by shifting section 52 longitudinally inwardly and outwardly on section 54, the sections 52 and 54 being moved relative to one another by adjustment screw 102 extending through member 104, the latter member being rigidly secured to section 52 by screws 1% and 108 extending through said member into section 52. After an adjustment has been made, nut 110 is tightened against member 104 to hold the two sections in their adjusted position.

In order to permit the grinding wheel to be withdrawn rapidly, a cam lever arrangement consisting of a cam mounted on shaft 122 engaging the inner side of member 104 is provided for urging body 56 inwardly or outwardly to place the grinding wheel in working position and withdraw it therefrom. Shaft 122 is operated to rotate cam 120 by a lever 124 secured to the upper end of the shaft. The body is kept in alignment with section 52 by groove 125 and key 126, and section 52 in alignment with section 54 by laterally disposed plates 127 and 128 secured by screws to section 52 and extending downwardly over the edge of section 54. A spring 129 may be used to assist in retaining the body in its operating position.

In order to mount the present thread grinding mechanism on the conventional lathe, a shoe 136 threadedly mounted on bolt 132 is provided for seating in the conventional transverse slot on compound rest 27 or carriage 26. After shoe 138 has been inserted in the slot on the carriage, bolt 132 is tightened sufliciently to hold the present thread grinding mechanism rigidly on the carriage.

One of the special features of the present thread grinding mechanism which assists in rendering it particularly adaptable for occasional use on the conventional lathe is the wheel dressing device 140-, consisting of a base 142 rigidly secured to platform 90 by one or more bolts 144 extending therethrough into the platform and a slidable dressing tool carriage 148 having a tool mounting recess 150 for receiving a conventional dressing tool 152 therein. The carriage 148 is provided with oppositely disposed tongues 154 and 156 on the upper and lower sides thereof seating in grooves 158 and 160, respectively, for dressing opposite sides of the wheel. In the use of this dressing device, tongue 156, for example, is placed in groove 160, and tool 152 is moved inwardly and outwardly over the edge of the wheel, and then the other side of the wheel is dressed by turning carriage 148 over, placing tongue 154 in groove 158, thereby placing tool 152 in position to engage the opposite side of the wheel. When the wheel dressing device is not in use, carriage 148 is removed from the device.

In order to assist in providing the desired rpm. for the work piece being threaded, the present mechanism includes a speed reducer mechanism 44 having a housing mounted on and secured to bed 20, and input shaft 172 for connection with the rotatable mandrel of the head stock and output shaft 174, The two shafts are coaxial and interconnected by gear 176 on the input shaft, gear 178 on the output shaft, and interconnecting idle gears 180 and 182 meshed with gears 176- and 178, respectively. The two idle gears are interconnected by reduction gears 184 and 186, the former meshing with gear 180 and the latter with 184. Gear 184 is journalled on an idle shaft 187 and gear 186 is mounted rigidly on shaft 188 on which gear 182 is mounted for rota-- tion in unison therewith. Output shaft 174 is mounted in bearing 189 and is telescoped into the input shaft, the" two shafts adapted to rotate relative to one another in the same direction on intervening bearings 190 and 192. The output shaft is mounted in bearing 194 which, together with bearings 189, 190 and 192, forms a substantially rigid structure in which the input and output shafts are adapted to rotate freely relative toone another. The

output shaft has a hollow center 196 for receiving a spindle or other tool for holding the work piece for the grinding operation. In using the present speed reducing unit, the speed is varied by the usual speed controls on the lathe, the reducer being provided primarily for a slower r.p.rn. which is often unobtainable on the less sophisticated conventional metal cutting lathe.

In the operation of the present thread grinding mechagrinding mechanism 42 must be withdrawn from the work piece at any position therealong, it may be done without disturbing the setting by the quick release controlled by lever 124 operating cam 12%. The quick release control may also be used after the thread cutting 7 operation has been completed in order to withdraw the wheel from the work piece and to permit the thread -grinding mechanism to be returned to its initial position for performing the next succeeding thread grinding operation.

While only one embodiment of the present invention has been described in detail herein, various changes and modifications may be made to suit requirements. 1

I claim:

1. In combination with a conventional metal cutting lathe having a bed, a power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a lower section mounted rigidly on the carriage and an upper section mounted on said lower section for vertical adjustment with respect to the work piece, an adjustment screw for moving said upper section and for retaining said sections in adjusted position, a body mounted on said base and slidable toward and away from the 'work piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its operating position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said upstanding portion on a ver{ tical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding wheel on one end of said mandrel, a motor mounted on said platform for driving said wheel,

pivot means for said platform including a slidable tongue and groove and having its pivot point at the center of said wheel, means for locking said platform in its adjusted position, a speed reducer unit having coaxial input and output shafts, said input shaft being axially aligned with and driven by the lathe spindle and said output shaft having a fixture for holding the work piece, a means for rigidly mounting said unit on the lathe bed, a grinding wheel dressing device mounted on said platform adjacent said wheel grinding means and including a base having straight intersecting grooves in the surface thereof forming an X-shape, and a carriage having a tongue on each side for seating and sliding in said grooves, said tongues being parallel and positioned in the same position on opposite surfaces of said last mentioned carriage, and a dressing tool mounted in one edge of said last mentioned carriage and extending transversely with respect to said tongues.

2. In combination with a conventional metal cutting lathe having a bed, a power driven head stock with spindle tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a lower section mounted rigidly on the carriage and an upper section mounted on said lower section for movement thereon, an adjustment screw for moving said upper section and for retaining said section in adjusted position, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said up standing portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding wheel on one end of said mandrel, a motor mounted on said plat form for driving said wheel, pivot means for said platform including a slidable tongue and groove and having its pivot point at the center of said wheel, means for locking said platform in its adjusted position, a speed reducer unit having coaxial input and output shafts, said input shaft being axially aligned with and driven by the lathe spindle and said output shaft having a fixture for holding the work piece, and a means for rigidly mounting said unit on the lathe bed.

3. In combination with a conventional metal cutting lathe having a bed, a power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a lower section mounted rigidly on the carriage and an upper section mounted on said lower section for movement toward and away from the work piece, an adjustment screw for moving said upper section and for retaining said section in adjusted position, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding wheel on one end of said mandrel, a motor mounted on said platform for driving said wheel pivot means for said platform including a slidable tongue and groove and having its pivot point at the center of said wheel, means for locking said platform in its adjusted position, a grinding wheel dressing device mounted on said platform adjacent said wheel grinding means and including a base having straight intersecting grooves in the surface thereof forming and X-shape, a carriage having a tongue on each side for seating and sliding in said grooves, said tongues being parallel and positioned in the same position on opposite surfaces of said last mentioned carriage, and a dressing tool mounted in one edge of said last mentioned carriage and extending transversely with respect to said tongues.

4. In combination with a conventional metal cutting lathe having a bed, a power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a lower section mounted rigidly on the carriage and an upper section mounted on said lower section for movement toward and away from the work piece, an adjustment screw for moving said upper section and for retaining said section in adjusted position, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding wheel on one end of said mandrel, a motor mounted on said platform for driving said wheel, pivot means for said platform including a slidable tongue and groove and having its pivot point at the center of said wheel, and means for locking said platform in its adjusted position.

5. For use in conjunction with a metal cutting lathe having a bed, power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a lower section mounted rigidly on the carriage and an upper section mounted on said lower section for movement toward and away from the work piece, an adjustment screw for moving said upper section and for retaining said section in adjusted position, a body mounted on said base and slidable toward and away from the wonk piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding wheel on said mandrel, and a motor mounted on said platform for driving said wheel.

6. For use in conjunction with a metal cutting lathe having a bed, a power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base having a low section mounted rigidly on the carriage and an upper section mounted on said lower section for movement toward and away from .the work piece, a means for moving said upper section and for retaining said section in adjusted position, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a

means for moving said body and for locking said body in its forward position, a lever for operating said last mention means, a plat-form pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding means on said mandrel, and a motor mounted on said platform for driving said grinding means.

7. For use in conjunction with a metal cutting lathe having a bed, power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base rigidly mounted on the carriage, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a cam means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned cam means, a platform pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journal-led on said platform extending parallel with the lathe bed, a grinding wheel on said mandrel, and a motor mounted on said platform for driving said grinding wheel.

8. For use in conjunction with a metal cutting lathe having a bed, power driven head stock with spindle, tail stock for holding a work piece and carriage on said bed: a thread grinding mechanism comprising a base rigidly mounted on the carriage, a body mounted on said base and slidable toward and away from the work piece and having a forwardly positioned upstanding portion, a means for moving said body and for locking said body in its forward position, a lever for operating said last mentioned means, a platform pivotally mounted on said upstanding portion on a vertical plane parallel with the lathe bed, a mandrel journalled on said platform extending parallel with the lathe bed, a grinding means on said mandrel, and a motor mounted on said platform for driving said grinding means.

References Cited in the file of this patent UNITED STATES PATENTS 1,355,710 Stryhal Oct. 12, 1920 1,579,691 Durkee Apr. 6, 1926 1,612,371 Gleason Dec. 28, 1926 2,415,121 Wiken et a1. Feb. 4, 1947 2,437,599 Greeley Mar. 9, 1948 I 2,495,107 Koenig Jan. 17, 1950 

2. IN COMBINATION WITH A CONVENTIONAL METAL CUTTING LATHE HAVING A BED, A POWER DRIVEN HEAD STOCK WITH SPINDLE TAIL STOCK FOR HOLDING A WORK PIECE AND CARRIAGE ON SAID BED: A THREAD GRINDING MECHANISM COMPRISING A BASE HAVING A LOWER SECTION MOUNTED RIGIDLY ON THE CARRIAGE AND AN UPPER SECTION MOUNTED ON SAID LOWER SECTION FOR MOVEMENT THEREON, AN ADJUSTMENT SCREW FOR MOVING SAID UPPER SECTION AND FOR RETAINING SAID SECTION IN ADJUSTED POSITION, A BODY MOUNTED ON SAID BASE AND SLIDABLE TOWARD AND AWAY FROM THE WORK PIECE AND HAVING A FORWARDLY POSITIONED UPSTANDING PORTION, A CAM MEANS FOR MOVING SAID BODY AND FOR LOCKING SAID BODY IN ITS FORWARD POSITION, A LEVER FOR OPERATING SAID LAST MENTIONED CAM MEANS, A PLATFORM PIVOTALLY MOUNTED ON SAID UPSTANDING PORTION ON A VERTICAL PLANE PARALLEL WITH THE LATHE BED, A MANDREL JOURNALLED ON SAID PLATFORM EX- 